<i>Objective:</i> Very few studies have assessed substance use in clinical samples of adolescents with eating disorders (ED). This paper reports the prevalence of regular or risky substance use (RRSU) and substance use disorder (SUD) in adolescents with ED. <i>Methods:</i> The Teen-Addiction Severity Index (T-ASI), the Youth Self-Report (YSR) scale and substance use questionnaires were administered to 95 adolescent patients aged 12–17 years who fulfilled the DSM-IV-TR diagnostic criteria for anorexia nervosa, bulimia nervosa and ED not otherwise specified. All patients were consecutively attended at an Eating Disorders Unit. <i>Results:</i> 14.7% presented SUD related to tobacco, 3.2% to cannabis, 1.1% to alcohol, and 1.1% to other substances. Patients with RRSU-SUD of any substance except tobacco were 34.7%. Patients with RRSU-SUD failed more subjects, repeated more school years and had higher scores on T-ASI scales of problems at school, family function and social relationships, and on YSR scales of delinquent behavior and externalizing problems. <i>Conclusions:</i> Substance use problems in ED adolescents are frequent and formal screening of them as well as a specific therapeutic approach are necessary.